The invention relates to a system for controlling power consumption at a user of electric power, especially a dwelling supplied with power from a power plant, comprising a control unit installed at the user and having a programmable memory for storage of data for controlling the power consumption, parameter-sensing sensors for the supply of input signals to the control unit, an electric meter communicating with the control unit for measuring the total instantaneous consumption of the user, and a number of addressable function nodes connected between the control unit and the various loads and being in both-way communication with the control unit, for connection and disconnection of power-consuming units under the control thereof, the memory of the control unit containing a program for controlling the power consumption based on an estimate of the instantaneous consumption, and the control unit being arranged to transmit addressed messages to the function nodes, so that only the nodes with the correct address receive the current messages and execute load-affecting actions based on the message content, to thereby reduce the instantaneous consumption.
For dwellings and households there have been launched, during the later years, a number of energy-economizing products and systems reducing the consumption of electric energy for the household. Generally, these systems are based on temperature or sequence control of electric appliances used for heating, for instance electric heating stoves. In this manner the power consumption is reduced at the end user, but the power consumption is not reduced during the period in which the load is largest.
Statistical data regarding the energy consumption in private households show that there is a higher consumption in some time periods during the day. These time periods are in the morning hours and in the afternoon/evening, respectively, and more specifically in the periods 6-10 and 16-23. Within a distribution area, the power load in the morning hours may rise from e.g. 825 MW to about 1100 MW around 8 o""clock, to sink thereafter before a new peak occurs in the evening around 19 o""clock. The most important thing is not the time at which the load peaks occur, but that they appear at intervals with a high degree of regularity in the course of the morning hours and the afternoon/evening. The load profile is approximately equal through the whole year, a normal year being assumed, i.e. that there are no extreme changes in temperature or in the prices of electricity.
From the collected statistical data, the energy plants know the load histories and prognosticate future consumption from predefined consumption curves and within given safety margins.
Today there exist different types of systems in which the power consumption at the subscribers of a power company is controlled. The traditional xe2x80x9cDemand Side Managementxe2x80x9d or DSM method is based on two-way communication between energy supplier (energy plant) and subscribers. In these systems, the framework conditions and the parameters for how the consumption in the dwelling of the subscriber is to be controlled, are set by the power plant. This method has the weakness that the system is based on often occurring input of regulating control data from the power company. These control data then will be based on the consumption pattern of the total subscriber mass of the power company. This consumption pattern may, however, deviate strongly from the consumption pattern of the individual household, so that the achieved control of the power consumption in many cases will not be optimal, considered in relation to the consumption pattern and the current power consumption at the individual subscriber or user.
Several other known methods and systems remedy this weakness, either intendedly or unintendedly, by putting in control mechanisms seeking an optimum local control at the subscribers. As examples hereof, reference can be made to U.S. Pat. Nos. 5,436,510, 4,510,398 and EP 0 717 487 A1 disclosing systems of the introductorily stated type. The local control according to these systems usually is based on said framework conditions which are given by the power company, but to a higher extent than traditional DSM control is able to secure a better utilization of the energy at the individual subscribers. Common to these systems is, however, that the dynamic load control limits itself to see to it that the power consumption at the subscriber does not exceed given maximum limits. The maximum limits may be set by the power company, or they may be set locally at the subscriber. The systems are quiescent as long as these limits are not exceeded. This means, for example, that if a given number of households at a given time lie closely under these limits, the collected total consumption for these households will be relatively high. U.S. Pat. No. 5,436,510 and U.S. Pat. No. 4,510,398 in addition describe devices seeking to add new loads as long as the total consumption is under the given maximum limit. In addition to said total consumption problems, this means that the subscriber hardly gets any pleasure from the power control with respect to energy saving.
On this background it is an object of the invention to provide a system distributing the power consumption at a subscriber even if the consumption at the subscriber does not exceed given maximum limits, so that, both locally at a subscriber and collectively in a larger user or subscriber mass, one achieves a more optimum power regulation and a smoother power distribution.
The above-mentioned object is achieved with a system of the introductorily stated type which, according to the invention, is characterized in that the control unit is a main unit arranged to control the power consumption also based on an estimate of a historical consumption pattern at the user, so that the instantaneous consumption is reduced both in the periods in which the power load at the user is highest, and in the periods in which the historical consumption pattern of the user dictates that there is a high load, and that the main unit is arranged to distribute the power consumption by means of a random function distributing the connection of the power-consuming units over a given time interval, the random function being independent of energy plants and other users.
In the system according to the invention the main unit is arranged to distribute the power consumption in the time periods around global and local high load by means of said random function which operates locally at a subscriber in such a manner that the power consumption is displaced a randomly chosen time interval, to flatten the local power consumption in addition to the collected or global total consumption for a whole user or subscriber mass as seen by the power company. In practice this means that one uses the xe2x80x9claw of large numbersxe2x80x9d to lower the power consumption in a larger transformer circuit with many connected subscribers. Thus, the system implies that several main units will appear in co-action without knowing about each other, and thereby keep the power consumption down on a global scale.
The system according to the invention from the starting point is not connected to an operating central, but is a stand-alone automatic control system monitoring and regulating the power consumption at the end user from a historical consumption pattern established by the end user/household during a previous time period, together with the instantaneous consumption, the temperature and other variable input signals.
Thus, the load distribution takes place locally in the household and is controlled by the main unit (hereafter also called xe2x80x9cmasterxe2x80x9d) utilizing such parameters as temperature, instantaneous consumption and known consumption patterns to accomplish the distribution, based on said random function. This will take place without the comfort being changed in the household. Said parameters are run through a set of rules stored in the program of the master. The program works out prognoses and distributes the power consumption based on season, day of the week, time of the day, temperature, the power consumption at the moment and the power consumption over time. As mentioned, the system operates as a self-contained unit and is not connected to a power plant or an operating central. Primarily, the system is intended for use in households, business buildings and other buildings which, for some reason, have a need for releasing and stabilizing the power consumption, so that the load peaks are reduced.
If desired, the system may for example be connected to an operating central by means of, e.g., a both-way communication system. Since the system provides for automatic power release in high-load periods and the power is distributed over the hours around peak load, the load structure is flattened and gets smaller variations. The energy plants then can prognosticate the power consumption with a smaller risk, carry out cost-effective readings, reduce the network loss by means of a smoother load, and also connect the customer/subscriber to themselves by offering additional services.